Several states as well as certain European nations have increasingly brought about stricter requirements for the sulfur content of petroleum fuel. Aside from reducing corrosion in engines, lower sulfur provides for cleaner air with reduced toxicity to human life. An example of the potential danger from air polluted with sulfur is the formation of acid rain from oxidized forms of sulfur.
Hydrodesulfurization is a catalytic chemical process used worldwide to remove sulfur from refined petroleum products. The process is carried out at elevated temperatures ranging from 300 to 400° C. with elevated pressures ranging from 30 to 130 atmospheres. A catalyst is usually employed and comprises an inert substrate containing cobalt and molybdenum. Prior to exposure to the catalyst, the sulfur rich feed is joined by a stream of hydrogen rich gas. In a typical reaction, ethyl mercaptan is converted to the hydrocarbon ethane plus hydrogen sulfide. Other organic sulfur containing compounds such as sulfides, disulfides, thiophene and thiophene derivatives are also converted to the corresponding hydrocarbon plus hydrogen sulfide, which is subsequently converted into elemental sulfur. Most of the sulfur produced worldwide is by-product sulfur from this refinery process.
Modification of the hydrodesulfurization process had been reported in the literature. For example, U.S. Pat. No. 5,770,047 to Salazar, et al. discloses a process for reducing sulfur content by 30 to 60%. The process requires the introduction of hydrogen gas at high temperatures in the range of 280 to 320° C. with best results achieved at a pressure of 400 psig. A special catalyst of Group III or Group VI metals impregnated within in a high surface area inert support was also required.
U.S. Pat. No. 8,062,322 to Schmidt discloses that desulfurization of sulfur containing fuels by a pyrolysis method conducted at a temperature of between 600° and 900° C. in the presence of a finely divided metal such as iron powder.
U.S. Pat. No. 480,885,662 to Mead discloses a process for producing low sulfur petroleum fuel. The process comprises the steps of contacting the fuel with an oxygen containing gas, mixing the fuel with acid and then neutralizing the acid with the base. The process requires temperatures of about 400° to 675° F.
The current state of the technology for desulfurization of petroleum fuel requires extremely high temperatures and pressures that require highly engineered, special equipment. Storage facilities and delivery equipment for hydrogen gas are often required components.
Sulfur continues to be a major offender in the pollution of air through the burning of fossil fuels. As concerns for the burning of fossil fuels is heightened among the major industrial countries of the world, sulfur continues to be a most undesirable component of fossil fuel burning, and consequently, permissible levels continue to be reduced.
There is a continuing need for new methods and alternate approaches for removing sulfur from petroleum fuel, and, in particular, manufacturers seek methods that are relatively simple, have low capital investment costs and are highly effective. The present invention meets or exceeds these needs.